The present invention relates to a separating apparatus and processing method for a member such as a bonded substrate stack, a semiconductor substrate manufacturing method, and a semiconductor device manufacturing method.
A substrate (SOI substrate) having an SOI (Silicon On Insulator) structure is known as a substrate having a single-crystal Si layer on an insulating layer. A device using this SOI substrate has many advantages that cannot be achieved by ordinary Si substrates. Examples of the advantages are as follows.
(1) The integration degree can be increased because dielectric isolation is easy.
(2) The radiation resistance can be increased.
(3) The operating speed of the device can be increased because the stray capacitance is small.
(4) No well step is necessary.
(5) Latch-up can be prevented.
(6) A fully depleted field effect transistor can be formed by thin film formation.
Since an SOI structure has the above various advantages, researches have been made on its formation method for several decades.
As a method, an SOI structure is formed by bonding a single-crystal Si substrate to another thermally oxidized single-crystal Si substrate by annealing or an adhesive. In this method, an active layer for forming a device must be uniformly thin. More specifically, a single-crystal Si substrate having a thickness of several hundred micron must be thinned down to the micron order or less.
To thin the substrate, polishing or selective etching can be used.
A single-crystal Si substrate can hardly be uniformly thinned by polishing. Especially, in thinning to the submicron order, the variation range is several ten %. As the wafer size becomes large, this difficulty becomes more pronounced.
The present applicant has disclosed a new SOI technique in Japanese Patent Laid-Open No. 5-21338. In this technique, a first substrate obtained by forming a porous layer on a single-crystal Si substrate and a non-porous single-crystal layer on its surface is bonded to a second substrate via an insulating layer. After this, the bonded substrate stack is separated into two substrates at the porous layer, thereby transferring the non-porous single-crystal layer to the second substrate. This technique is advantageous because the film thickness uniformity of the SOI layer is good, the crystal defect density in the SOI layer can be decreased, the surface planarity of the SOI layer is good, no expensive manufacturing apparatus with special specifications is required, and SOI substrates having about several hundred-xc3x85 to 10-xcexcm thick SOI films can be manufactured by a single manufacturing apparatus.
To separate the bonded first and second substrates into two substrates without breaking the first and second substrates, the following methods are available: the two substrates are pulled in opposite directions while applying a force in a direction perpendicular to the bonding interface; a shearing force is applied parallel to the bonding interface (for example, the two substrates are moved in opposite directions in a plane parallel to the bonding interface, or the two substrates are rotated in opposite directions while applying a force in the circumferential direction); pressure is applied in a direction perpendicular to the bonding interface; a wave energy such as an ultrasonic wave is applied to the separation region; a peeling member (e.g., a sharp blade such as a knife) is inserted into the separation region parallel to the bonding interface from the side surface side of the bonded substrate stack; the expansion energy of a substance filling the pores of the porous layer functioning as the separation region is used; the porous layer functioning as the separation region is thermally oxidized from the side surface of the bonded substrate stack to expand the volume of the porous layer and separate the substrates; and the porous layer functioning as the separation region is selectively etched from the side surface of the bonded substrate stack to separate the substrates.
As a method of separating a bonded substrate stack, the present applicant disclosed an epoch-making technique in Japanese Patent Laid-Open No. 11-45840 (Japanese Patent No. 2,877,800). In the separating method described in Japanese Patent Laid-Open No. 11-45840, a bonded substrate stack having a porous layer or ion implantation layer serving as a separation layer is separated into two substrates by injecting a fluid into the side surface of the bonded substrate.
More specifically, in the separating method described in Japanese Patent Laid-Open No. 11-45840, the bonded substrate stack is held by a pair of holders (substrate holding portions) having a smaller size than that of the bonded substrate stack. A fluid is injected into the side surface of the bonded substrate stack while rotating it, thereby separating the bonded substrate stack into two substrates at the porous layer.
In holding the bonded substrate stack by the pair of holders, which have a size smaller than that of the bonded substrate stack, distortion may occur at the outer portion due to its own weight or the like, or the bonded substrate stack may be held with some distortion which has occurred in the manufacturing process remaining without being corrected. Assume that distortion exists in the bonded substrate stack held by holders. In this case, when a fluid is to be injected throughout the perimeter of the bonded substrate stack while rotating it, the fluid maybe injected to a position deviated from an appropriate position (e.g., a bonding interface or separation layer).
For the sake of easy understanding, an extreme case will be described. For example, if the bonded substrate stack is largely distorted, a fluid ejected from a nozzle, the position of which has been adjusted on the assumption that the bonded substrate stack is not distorted, is not injected into the separation layer or bonding interface of the bonded substrate stack. When this occurs, separation processing may not progress at all. This will be described with reference to FIG. 13.
FIG. 13 is a view showing a state wherein a bonded substrate stack 50 which is largely distorted is separated into two substrates at a separation layer 12. In the example shown in FIG. 13, the position of the actual separation layer 12 largely deviates from that of a separation layer without any distortion (the ideal position of the separation layer). In this case, the position of a nozzle 120 is adjusted on the assumption that the separation layer 12 is arranged at the ideal position. When separation is performed in this state, a fluid from the nozzle 120 is not injected into the separation layer 12, thereby preventing smooth separation. If large distortion exists at the perimeter of the bonded substrate stack 50, separation does not progress speedily. This may result in unsatisfactory separation.
The probability of the above-described unsatisfactory separation would increasingly become higher due to increase in size of a bonded substrate stack along with increase in size of a required SOI substrate.
In addition, in holding a bonded substrate stack by holders, some foreign substance may enter between the bonded substrate stack and holders. In this case as well, a fluid from a nozzle may be injected into a position deviated from the separation layer or bonding interface of the bonded substrate stack.
The present invention has been made in consideration of the above situation, and has as its object to guarantee that in separating a member having a separation layer such as a bonded substrate stack, the member be appropriately separated regardless of some distortion in the member, insufficient accuracy in holding the member, or the like.
According to the present invention, there is provided a method of separating a member which has a separation layer inside using a jet, characterized by comprising the control step of, halfway through separation processing of the member, changing a positional relationship between a jet orbit and the member in accordance with a program which is set in advance before start of the separation processing.
According to a preferred aspect of the present invention, in the control step, the positional relationship between the jet orbit and the member is preferably changed stepwise in accordance with the program.
According to a preferred aspect of the present invention, the program is preferably a single program which is set in advance to apply to separation of a plurality of members.
According to a preferred aspect of the present invention, in the control step, for example, the jet orbit or a position of the member is changed in a direction perpendicular to the separation layer of the member halfway through the separation processing.
According to a preferred aspect of the present invention, in the control step, for example, a direction of the jet is changed halfway through the separation processing.
According to a preferred aspect of the present invention, in the control step, for example, the positional relationship between the jet orbit and the member is changed halfway through the separation processing by switching an ejecting portion out of a plurality of ejecting portions, which is used to inject a fluid into the member.
According to a preferred aspect of the present invention, for example, this separating method is suitable for separation of the member which has a recessed portion in an outer side of the separation layer and has a distortion within a predetermined range, and in the control step, the positional relationship between the jet orbit and the member is so changed halfway through the separation processing as to cause the jet to strike on the recessed portion almost throughout a perimeter of the recessed portion before the separation processing is complete.
Alternatively, this separating method is suitable for separation of the member which has a recessed portion in an outer side of the separation layer and has a distortion within a predetermined range, and in the control step, a change in the positional relationship between the jet orbit and the member is repeated until the jet strikes on the recessed portion almost throughout a perimeter of the recessed portion.
According to a preferred aspect of the present invention, the control step preferably comprises the step of fixing the positional relationship between the jet orbit and the member after the jet strikes on the recessed portion almost throughout the perimeter of the recessed portion.
According to a preferred aspect of the present invention, the member is preferably rotated about an axis perpendicular to the separation layer during the separation processing.
According to a preferred aspect of the present invention, this separating method is suitable for separation of a bonded substrate stack, obtained by bonding to a handle substrate a seed substrate which has a semiconductor layer on a separation layer through an insulating layer, at the separation layer.
According to a preferred aspect of the present invention, for example, the jet is obtained by ejecting a liquid or gas from an ejecting portion.
According to the present invention, there is provided an apparatus for separating a member which has a separation layer inside using a jet, characterized by comprising a holding portion for holding a member, an ejecting nozzle for forming jets, and a controller for changing, halfway through separation processing of the member held by the holding portion, a positional relationship between an orbit of the jet and the member in accordance with a program which is set in advance.
According to a preferred aspect of the present invention, the controller preferably changes the positional relationship between the jet orbit and the member stepwise in accordance with the program.
According to a preferred aspect of the present invention, the program is preferably a single program which is set in advance to apply to separation of a plurality of members.
According to a preferred aspect of the present invention, for example, the controller changes the jet orbit or a position of the member in a direction perpendicular to the separation layer of the member halfway through the separation processing.
According to a preferred aspect of the present invention, for example, the controller changes a direction of the jet halfway through the separation processing.
According to a preferred aspect of the present invention, for example, the controller changes the positional relationship between the jet orbit and the member halfway through the separation processing by switching an ejecting portion out of a plurality of ejecting portions, which is used to inject a fluid into the member.
According to a preferred aspect of the present invention, this separating apparatus is suitable for separation of the member which has a recessed portion in an outer side of the separation layer and has a distortion within a predetermined range, and the controller preferably so changes the positional relationship between the jet orbit and the member halfway through the separation processing as to cause the jet to strike on the recessed portion almost throughout a perimeter of the recessed portion before the separation processing is complete.
Alternatively, this separating apparatus is suitable for separation of the member which has a recessed portion in an outer side of the separation layer and has a distortion within a predetermined range, and the controller preferably repeats a change in the positional relationship between the jet orbit and the member until the jet strikes on the recessed portion almost throughout the perimeter of the recessed portion.
According to a preferred aspect of the present invention, the controller preferably fixes the positional relationship between the jet orbit and the member after the jet strikes on the recessed portion almost throughout the perimeter of the recessed portion.
According to a preferred aspect of the present invention, this separating apparatus preferably further comprises a rotating mechanism for rotating the member about an axis perpendicular to the separation layer during the separation processing.
According to a preferred aspect of the present invention, this separating apparatus is suitable for separation of a bonded substrate stack obtained by bonding to a handle substrate a seed substrate which has a semiconductor layer on a separation layer through an insulating layer.
According to a preferred aspect of the present invention, for example, the jet is obtained by ejecting a liquid or gas from an ejecting portion.
According to the present invention, there is provided a semiconductor substrate manufacturing method characterized by comprising the steps of forming a bonded substrate stack as a member to be separated by bonding to a second substrate a first substrate which has a separation layer inside and a transfer layer on the separation layer, and separating the bonded substrate stack at the separation layer by using the above separating method.
According to the present invention, there is provided a semiconductor device manufacturing method characterized by comprising the steps of preparing an SOI substrate manufactured using the above manufacturing method, and element-isolating an SOI layer of the SOI substrate and forming a transistor on the element-isolated SOI layer.
The transistor may be a partially depleted FET or fully depleted FET.
According to the present invention, there is provided another method of separating a member which has a separation layer inside using a jet, characterized in that separation is performed using an orbit of a first jet and an orbit of a second jet which are set in advance before separation processing and have positions different from each other in a direction of thickness of the member.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.